초록
<P><B>Abstract</B></P> <P>In this study, batch biohydrogen production by co-digestion of raw rice straw and activated sewage sludge was investigated with different inoculum heat treatment, pH, S/X ratio (based on VS) and substrate sizes under mesophilic condition. In order to achieve a high bio-hydrogen yield and methanogens activity inhibition, heat treatment of inoculum was optimized at different exposure times (30, 45 & 60 min) and temperature ranges (80, 90 and 100 °C) prior to dark fermentation process. Collected data was analysed using response surface methodology (RSM). The heat treatment of inoculum at 100 °C for 60 min produced the highest bio-hydrogen yield of 14.22 NmL H<SUB>2</SUB>/g VS at concentration of 70.97% and Production of 0.073 NmL CH<SUB>4</SUB>/g VS at 0.17% concentration in total produced biogas. The raw rice straw was also co-digested with heat-treated inoculum at different ratios of volatile solids (2:1, 4:1 and 6:1) and initial pH (4, 4.75 and 5.5) as numerical variables and 4 categories of substrate size ((250–500 μm], (500 μm-2mm], (2–20 mm), [20–30 mm]). The highest bio-hydrogen yield of 14.70 NmL/g VS was recognized at the optimum initial pH of 5.01 and S/X ratio of 4.54:1 using 2–20 mm rice straw.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Enhancement of mesophilic bio-hydrogen production by amending different factors. </LI> <LI> Highest bio-hydrogen production yield of 14.54 ± 0.29 ml H<SUB>2</SUB>/g VS was achieved. </LI> <LI> Substrate size reduction to less than 2 mm had negative effect on bio-hydrogen yield. </LI> </UL> </P>